This invention relates to blood cell classification systems and more particularly to improvements therein.
A system for classifying the various major types of white blood cells in the blood is of urgent need in the area of automated clinical laboratory determinations. In the United States alone, more than a million such determinations are performed in hospital laboratories each day. At present, these are done by relatively unskilled technicians, and studies by the National Center For Disease Control have shown that results are often unreliable. Since this determination, often referred to as a differential white blood cell (WBC) count, is a main stay of clinical laboratory diagnosis, an instrument that would perform it accurately, quickly and at relatively low cost, would represent a significant advance in laboratory medicine. Extensions of the technique to classify exfoliated cervical cells for preliminary indications of cancer would make the instrument even more valuable. Two basic approaches are being taken at present, but as yet an automatic device that provides rapid results with good statistical validity at a cost competitive with those of classification with human technologists does not exist.
The first approach involves comparing a microscope image, using pattern recognition techniques, with the data in the memory of the computer, whereby the various cells within the field of view are inspected. The problem with this approach is its expense and its slow speed. A computer system and peripherals are required and the speed with which the cells can be processed is on the order of that attainable by a human technologist (i.e., 1 per second).
A second approach, and one which is inherently more effective, is one in which cells are introduced on the central line of a tube flowing liquid and are characterized down stream on the basis of size, fluorescent emission, or light absorption measurements, carried out using laser illumination. Classification speed is considerably higher than that attainable with the pattern recognition approach and is on the order of 1,000 cells per second. Little information is drawn from the limited number of measurements to pin point minor differences among white blood cells, and subtleties of classification are realistically traded off with the increased speed and improved statistics.